Many different types of performance improving devices including a wide variety of hydrofoil and/or stabilizer devices have been constructed and used to improve the overall performance of a particular watercraft. Some of the known hydrofoil/stabilizer devices utilized to facilitate on-plane operation are mounted directly to the stern of a watercraft whereas others are mounted to various portions of an outboard motor or stern drive unit including to the cavitation plate of the lower drive unit. Importantly, however, all of the known prior art devices which attach to the cavitation plate are attachable to either the topside and/or side edge portions of such cavitation plate. These known mounting arrangements cause fatigue and stress problems both with respect to the cavitation plate as well as the hydrofoil/stabilizer device attached thereto in that the upward force generated by the waterflow against the bottom portion of such known devices creates an upward thrust pressure which is constantly pulling the hydrofoil/stabilizer device upward and away from the top and side edge portions of the cavitation plate. This causes considerable stress at the points of joinder and eventually results in cracks in the cavitation plate and ultimate fatigue failure. Also, the known mounting arrangements for attaching the known devices to the topside and/or side edge portions of the cavitation plate do not provide, in many instances, sufficient overlap between the hydrofoil/stabilizer device and the cavitation plate to withstand the separation forces generated during boat operation, particularly at top end speeds. This is not true of the present device which mounts to the underside portion of the cavitation plate substantially across the entire bottom surface area thereof. None of the known prior art devices are attachable to the underside portion of the cavitation plate associated with outboard motors and stern drive units.
Also, many of the known prior art devices which facilitate on-plane boat operation are, in fact, hydrofoils and these devices operate on aerodynamic principles to create a higher pressure on the underside of the hydrofoil surface thereby generating lift which forces the stern of the boat up and the bow down. In order to generate sufficient lift over the top of the hydrofoil device, much higher boat speeds and much higher motor RPMS are required. This usually translates into using substantial throttle, if not full throttle, in order to generate sufficient waterflow over the hydrofoil device to generate sufficient lift to put the watercraft on-plane. This is not true of the present device which does not operate on aerodynamic principles but, instead, operates on the principle that water pressure hitting the bottom portion of the present plate-like device produces a resultant upward force on the plate member which is transferred to the stern of the boat thereby bringing the bow down to an on-plane condition. Since a pressure differential to produce hydrofoil lift is not required between the upper and lower surfaces of the present device, the present device requires less power and less speed to bring a watercraft up out-of-the-hole from a standstill position to an on-plane condition. For these and other reasons, the known prior art devices for facilitating on-plane operation of a watercraft have not been totally satisfactory.